2 constants, snippet_opt, snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg,
5 use if_chain::if_chain;
6 use rustc::declare_lint_pass;
7 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
8 use rustc_data_structures::fx::FxHashMap;
9 use rustc_errors::Applicability;
10 use rustc_session::declare_tool_lint;
12 use syntax::source_map::Span;
13 use syntax::visit::{walk_expr, FnKind, Visitor};
15 declare_clippy_lint! {
16 /// **What it does:** Checks for structure field patterns bound to wildcards.
18 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
19 /// the fields that are actually bound.
21 /// **Known problems:** None.
25 /// let { a: _, b: ref b, c: _ } = ..
27 pub UNNEEDED_FIELD_PATTERN,
29 "struct fields bound to a wildcard instead of using `..`"
32 declare_clippy_lint! {
33 /// **What it does:** Checks for function arguments having the similar names
34 /// differing by an underscore.
36 /// **Why is this bad?** It affects code readability.
38 /// **Known problems:** None.
42 /// fn foo(a: i32, _a: i32) {}
44 pub DUPLICATE_UNDERSCORE_ARGUMENT,
46 "function arguments having names which only differ by an underscore"
49 declare_clippy_lint! {
50 /// **What it does:** Detects closures called in the same expression where they
53 /// **Why is this bad?** It is unnecessarily adding to the expression's
56 /// **Known problems:** None.
62 pub REDUNDANT_CLOSURE_CALL,
64 "throwaway closures called in the expression they are defined"
67 declare_clippy_lint! {
68 /// **What it does:** Detects expressions of the form `--x`.
70 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
73 /// **Known problems:** None.
82 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
85 declare_clippy_lint! {
86 /// **What it does:** Warns on hexadecimal literals with mixed-case letter
89 /// **Why is this bad?** It looks confusing.
91 /// **Known problems:** None.
95 /// let y = 0x1a9BAcD;
97 pub MIXED_CASE_HEX_LITERALS,
99 "hex literals whose letter digits are not consistently upper- or lowercased"
102 declare_clippy_lint! {
103 /// **What it does:** Warns if literal suffixes are not separated by an
106 /// **Why is this bad?** It is much less readable.
108 /// **Known problems:** None.
112 /// let y = 123832i32;
114 pub UNSEPARATED_LITERAL_SUFFIX,
116 "literals whose suffix is not separated by an underscore"
119 declare_clippy_lint! {
120 /// **What it does:** Warns if an integral constant literal starts with `0`.
122 /// **Why is this bad?** In some languages (including the infamous C language
124 /// family), this marks an octal constant. In Rust however, this is a decimal
125 /// constant. This could
126 /// be confusing for both the writer and a reader of the constant.
128 /// **Known problems:** None.
136 /// println!("{}", a);
140 /// prints `123`, while in C:
143 /// #include <stdio.h>
147 /// printf("%d\n", a);
151 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
152 pub ZERO_PREFIXED_LITERAL,
154 "integer literals starting with `0`"
157 declare_clippy_lint! {
158 /// **What it does:** Warns if a generic shadows a built-in type.
160 /// **Why is this bad?** This gives surprising type errors.
162 /// **Known problems:** None.
167 /// impl<u32> Foo<u32> {
168 /// fn impl_func(&self) -> u32 {
173 pub BUILTIN_TYPE_SHADOW,
175 "shadowing a builtin type"
178 declare_clippy_lint! {
179 /// **What it does:** Checks for patterns in the form `name @ _`.
181 /// **Why is this bad?** It's almost always more readable to just use direct
184 /// **Known problems:** None.
188 /// # let v = Some("abc");
192 /// y @ _ => (), // easier written as `y`,
195 pub REDUNDANT_PATTERN,
197 "using `name @ _` in a pattern"
200 declare_clippy_lint! {
201 /// **What it does:** Checks for tuple patterns with a wildcard
202 /// pattern (`_`) is next to a rest pattern (`..`).
204 /// _NOTE_: While `_, ..` means there is at least one element left, `..`
205 /// means there are 0 or more elements left. This can make a difference
206 /// when refactoring, but shouldn't result in errors in the refactored code,
207 /// since the wildcard pattern isn't used anyway.
208 /// **Why is this bad?** The wildcard pattern is unneeded as the rest pattern
209 /// can match that element as well.
211 /// **Known problems:** None.
215 /// # struct TupleStruct(u32, u32, u32);
216 /// # let t = TupleStruct(1, 2, 3);
219 /// TupleStruct(0, .., _) => (),
223 /// can be written as
225 /// # struct TupleStruct(u32, u32, u32);
226 /// # let t = TupleStruct(1, 2, 3);
229 /// TupleStruct(0, ..) => (),
233 pub UNNEEDED_WILDCARD_PATTERN,
235 "tuple patterns with a wildcard pattern (`_`) is next to a rest pattern (`..`)"
238 declare_lint_pass!(MiscEarlyLints => [
239 UNNEEDED_FIELD_PATTERN,
240 DUPLICATE_UNDERSCORE_ARGUMENT,
241 REDUNDANT_CLOSURE_CALL,
243 MIXED_CASE_HEX_LITERALS,
244 UNSEPARATED_LITERAL_SUFFIX,
245 ZERO_PREFIXED_LITERAL,
248 UNNEEDED_WILDCARD_PATTERN,
251 // Used to find `return` statements or equivalents e.g., `?`
252 struct ReturnVisitor {
259 Self { found_return: false }
263 impl<'ast> Visitor<'ast> for ReturnVisitor {
264 fn visit_expr(&mut self, ex: &'ast Expr) {
265 if let ExprKind::Ret(_) = ex.kind {
266 self.found_return = true;
267 } else if let ExprKind::Try(_) = ex.kind {
268 self.found_return = true;
275 impl EarlyLintPass for MiscEarlyLints {
276 fn check_generics(&mut self, cx: &EarlyContext<'_>, gen: &Generics) {
277 for param in &gen.params {
278 if let GenericParamKind::Type { .. } = param.kind {
279 let name = param.ident.as_str();
280 if constants::BUILTIN_TYPES.contains(&&*name) {
285 &format!("This generic shadows the built-in type `{}`", name),
292 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &Pat) {
293 if let PatKind::Struct(ref npat, ref pfields, _) = pat.kind {
298 .expect("A path must have at least one segment")
302 for field in pfields {
303 if let PatKind::Wild = field.pat.kind {
307 if !pfields.is_empty() && wilds == pfields.len() {
310 UNNEEDED_FIELD_PATTERN,
312 "All the struct fields are matched to a wildcard pattern, consider using `..`.",
313 &format!("Try with `{} {{ .. }}` instead", type_name),
318 let mut normal = vec![];
320 for field in pfields {
321 match field.pat.kind {
324 if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
330 for field in pfields {
331 if let PatKind::Wild = field.pat.kind {
336 UNNEEDED_FIELD_PATTERN,
338 "You matched a field with a wildcard pattern. Consider using `..` instead",
343 UNNEEDED_FIELD_PATTERN,
345 "You matched a field with a wildcard pattern. Consider using `..` \
347 &format!("Try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
355 if let PatKind::Ident(_, ident, Some(ref right)) = pat.kind {
356 if let PatKind::Wild = right.kind {
362 "the `{} @ _` pattern can be written as just `{}`",
363 ident.name, ident.name,
366 format!("{}", ident.name),
367 Applicability::MachineApplicable,
372 check_unneeded_wildcard_pattern(cx, pat);
375 fn check_fn(&mut self, cx: &EarlyContext<'_>, _: FnKind<'_>, decl: &FnDecl, _: Span, _: NodeId) {
376 let mut registered_names: FxHashMap<String, Span> = FxHashMap::default();
378 for arg in &decl.inputs {
379 if let PatKind::Ident(_, ident, None) = arg.pat.kind {
380 let arg_name = ident.to_string();
382 if arg_name.starts_with('_') {
383 if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
386 DUPLICATE_UNDERSCORE_ARGUMENT,
389 "`{}` already exists, having another argument having almost the same \
390 name makes code comprehension and documentation more difficult",
391 arg_name[1..].to_owned()
396 registered_names.insert(arg_name, arg.pat.span);
402 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
403 if in_external_macro(cx.sess(), expr.span) {
407 ExprKind::Call(ref paren, _) => {
408 if let ExprKind::Paren(ref closure) = paren.kind {
409 if let ExprKind::Closure(_, _, _, ref decl, ref block, _) = closure.kind {
410 let mut visitor = ReturnVisitor::new();
411 visitor.visit_expr(block);
412 if !visitor.found_return {
415 REDUNDANT_CLOSURE_CALL,
417 "Try not to call a closure in the expression where it is declared.",
419 if decl.inputs.is_empty() {
420 let mut app = Applicability::MachineApplicable;
422 snippet_with_applicability(cx, block.span, "..", &mut app).into_owned();
423 db.span_suggestion(expr.span, "Try doing something like: ", hint, app);
431 ExprKind::Unary(UnOp::Neg, ref inner) => {
432 if let ExprKind::Unary(UnOp::Neg, _) = inner.kind {
437 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op",
441 ExprKind::Lit(ref lit) => Self::check_lit(cx, lit),
446 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
447 for w in block.stmts.windows(2) {
449 if let StmtKind::Local(ref local) = w[0].kind;
450 if let Option::Some(ref t) = local.init;
451 if let ExprKind::Closure(..) = t.kind;
452 if let PatKind::Ident(_, ident, _) = local.pat.kind;
453 if let StmtKind::Semi(ref second) = w[1].kind;
454 if let ExprKind::Assign(_, ref call) = second.kind;
455 if let ExprKind::Call(ref closure, _) = call.kind;
456 if let ExprKind::Path(_, ref path) = closure.kind;
458 if ident == path.segments[0].ident {
461 REDUNDANT_CLOSURE_CALL,
463 "Closure called just once immediately after it was declared",
472 impl MiscEarlyLints {
473 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
474 // We test if first character in snippet is a number, because the snippet could be an expansion
475 // from a built-in macro like `line!()` or a proc-macro like `#[wasm_bindgen]`.
476 // Note that this check also covers special case that `line!()` is eagerly expanded by compiler.
477 // See <https://github.com/rust-lang/rust-clippy/issues/4507> for a regression.
478 // FIXME: Find a better way to detect those cases.
479 let lit_snip = match snippet_opt(cx, lit.span) {
480 Some(snip) if snip.chars().next().map_or(false, |c| c.is_digit(10)) => snip,
484 if let LitKind::Int(value, lit_int_type) = lit.kind {
485 let suffix = match lit_int_type {
486 LitIntType::Signed(ty) => ty.name_str(),
487 LitIntType::Unsigned(ty) => ty.name_str(),
488 LitIntType::Unsuffixed => "",
491 let maybe_last_sep_idx = lit_snip.len() - suffix.len() - 1;
492 // Do not lint when literal is unsuffixed.
493 if !suffix.is_empty() && lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
496 UNSEPARATED_LITERAL_SUFFIX,
498 "integer type suffix should be separated by an underscore",
500 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
501 Applicability::MachineApplicable,
505 if lit_snip.starts_with("0x") {
506 let mut seen = (false, false);
507 for ch in lit_snip.as_bytes()[2..=maybe_last_sep_idx].iter() {
509 b'a'..=b'f' => seen.0 = true,
510 b'A'..=b'F' => seen.1 = true,
513 if seen.0 && seen.1 {
516 MIXED_CASE_HEX_LITERALS,
518 "inconsistent casing in hexadecimal literal",
523 } else if lit_snip.starts_with("0b") || lit_snip.starts_with("0o") {
525 } else if value != 0 && lit_snip.starts_with('0') {
528 ZERO_PREFIXED_LITERAL,
530 "this is a decimal constant",
534 "if you mean to use a decimal constant, remove the `0` to avoid confusion",
535 lit_snip.trim_start_matches(|c| c == '_' || c == '0').to_string(),
536 Applicability::MaybeIncorrect,
540 "if you mean to use an octal constant, use `0o`",
541 format!("0o{}", lit_snip.trim_start_matches(|c| c == '_' || c == '0')),
542 Applicability::MaybeIncorrect,
547 } else if let LitKind::Float(_, LitFloatType::Suffixed(float_ty)) = lit.kind {
548 let suffix = float_ty.name_str();
549 let maybe_last_sep_idx = lit_snip.len() - suffix.len() - 1;
550 if lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
553 UNSEPARATED_LITERAL_SUFFIX,
555 "float type suffix should be separated by an underscore",
557 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
558 Applicability::MachineApplicable,
565 fn check_unneeded_wildcard_pattern(cx: &EarlyContext<'_>, pat: &Pat) {
566 if let PatKind::TupleStruct(_, ref patterns) | PatKind::Tuple(ref patterns) = pat.kind {
567 fn span_lint(cx: &EarlyContext<'_>, span: Span, only_one: bool) {
570 UNNEEDED_WILDCARD_PATTERN,
573 "this pattern is unneeded as the `..` pattern can match that element"
575 "these patterns are unneeded as the `..` pattern can match those elements"
577 if only_one { "remove it" } else { "remove them" },
579 Applicability::MachineApplicable,
583 #[allow(clippy::trivially_copy_pass_by_ref)]
584 fn is_wild<P: std::ops::Deref<Target = Pat>>(pat: &&P) -> bool {
585 if let PatKind::Wild = pat.kind {
592 if let Some(rest_index) = patterns.iter().position(|pat| pat.is_rest()) {
593 if let Some((left_index, left_pat)) = patterns[..rest_index]
600 span_lint(cx, left_pat.span.until(patterns[rest_index].span), left_index == 0);
603 if let Some((right_index, right_pat)) =
604 patterns[rest_index + 1..].iter().take_while(is_wild).enumerate().last()
608 patterns[rest_index].span.shrink_to_hi().to(right_pat.span),